An electronic component, which is represented by a semiconductor element, is bonded to a substrate which supports the electronic component. The electronic component bonded to the substrate is mounted on another substrate such as a mounting board. Many of the electronic components are hermetically sealed within a package provided with a substrate in order to enhance the reliability of the electronic components. Such a substrate or a package needs to be stable against a temperature during bonding or operation of the electronic component. Accordingly, a plurality of members which constitute such a substrate or a package is joined using a silver solder having a melting point higher than a bonding temperature of the electronic component normally, for example.
In general, the substrate or the package is a complex which includes a circuit element for use of input/output of a signal or power supply from a power source, and a heat radiation element for radiating heat from an electronic component to outside. Members constituting such a complex may have different linear expansion coefficients. When the members are assembled by a silver solder under a high temperature, a warp or a strain is generated in the members due to the difference of the linear expansion coefficients of the members. The warp or strain deteriorates a characteristic of an electronic component, and lowers the reliability of the electronic component. Thus, it is needed to present a joined structural body of members and a method of joining members which are stable against a temperature during bonding or operation of an electronic component and can suppress warp and strain.